A clincher is a fact or argument that finally proves something, settles a dispute, or helps someone achieve a victory.
例句
DNA fingerprinting has proved the clincher in this investigation...在這次調查中,DNA指紋鑒定起了決定性的作用。The clincher was City's second goal, scored minutes from the end.離比賽結束還剩幾分鐘的時候，曼城隊的第二粒進球鎖定了勝局。
英英詞典釋義
Noun
1. an argument that is conclusive
2. a point or fact or remark that settles something conclusively